Enteropathogenic and enterohaemorrhagic Escherichia coli : more subversive elements

Enteropathogenic (EPEC) and enterohaemorrhagic Escherichia coli (EHEC) constitute a significant risk to human health worldwide. Both pathogens colonize the intestinal mucosa and, by subverting intestinal epithelial cell function, produce a characteristic histopathological feature known as the 'attaching and effacing' (A/E) lesion. Although EPEC was the first E. coli to be associated with human disease in the 1940s and 1950s, it was not until the late 1980s and early 1990s that the mechanisms and bacterial gene products used to induce this complex brush border membrane lesion and diarrhoeal disease started to be unravelled. During the past few months, there has been a burst of new data that have revolutionized some basic concepts of the molecular basis of bacterial pathogenesis in general and EPEC pathogenesis in particular. Major breakthroughs and developments in the genetic basis of A/E lesion formation, signal transduction, protein translocation, host cell receptors and intestinal colonization are highlighted in this review.     

Solar activity cycle and the incidence of foetal chromosome abnormalities detected at prenatal diagnosis

We studied 2001 foetuses during the period of minimal solar activity of solar cycle 21 and 2265 foetuses during the period of maximal solar activity of solar cycle 22, in all women aged 37 years and over who underwent free prenatal diagnosis in four hospitals in the greater Tel Aviv area. There were no significant differences in the total incidence of chromosomal abnormalities or of trisomy between the two periods (2.15% and 1.8% versus 2.34% and 2.12%, respectively). However, the trend of excessive incidence of chromosomal abnormalities in the period of maximal solar activity suggests that a prospective study in a large population would be required to rule out any possible effect of extreme solar activity.     

Depolarization exposes the voltage sensor of the sodium channels to the extracellular region

Summary Two domains of Na channels were mapped with site-specific antibodies raised in rabbit against synthetic peptides corresponding to a part of the voltage sensor of internal repeat 1C ₁ ⁺ (amino acids 210–223) and to a region designated dipole (amino acids 1690–1699) of eel electroplax sodium channels. The antibodies bind to their respective domains in both purified and membrane-bound channels and immunoprecipitate the channels from eel electroplax and rat brain synaptosomes.Anti-C ₁ ⁺ depresses the action potential of rat sciatic nerve in a concentration-dependent way. It binds to the external side of rat brain synaptosomal vesicle, and its binding is potentiated by depolarization. Anti-dipole binds to the inner side of the vesicle, and the binding is inhibited by depolarization.We are most grateful to Dr. M.T. Tosteson (Harvard Medical School) for providing us with samples of the S₄IV peptides. We wish to express our gratitude to Drs. D. Gordon (Hebrew University) and A. Safran (The Weizmann Institute) for helping in the immunoprecipitation procedure, to Drs. H. Rahamimoff (Hebrew University) and A. Barzilai (Columbia University) for advising us with the vesicle experiments, to Drs. D. Kassel and M. Gavish (Technion) for many fruitful discussions, and to Dr. Y. Palti (Technion) for discussions of electric field and suggesting the dipole peptide. This work was supported by a basic research fund (BRF) of The Israel Academy of Sciences #430.87 (H.M. and G.S.), a BSF Grant #84-00367 (H.M.) and The Henry Gutwirt Fund for the Promotion of Research-Technion VPR Fund #184-0093 (H.M.).     

Integrated Use of Organic and Bio-fertilizers to Improve Yield and Fruit Quality of Olives Grown in Low Fertility Sandy Soil in an Arid Environment

Olive productivity should be improved through stimulating nutrition, particularly under poor fertility soils. Consequently, the objective of this study was to assess the efficacy of applying organic and bio-fertilizers on the physiological growth, yield and fruit quality of olive trees under newly reclaimed poor-fertility sandy soil in an arid environment. During a field experiment carried out at El-Qantara, North Sinai, Egypt over two consecutive seasons (2019–2020 and 2020–2021), olive Kalamata trees were evaluated under three organic fertilizer treatments alone or in combination with three bio-fertilizers treatments. Organic fertilizer was applied as goat manure (16.8 kg/tree/year), or olive pomace (8.5 kg/tree/year) in mid-December of each season vs. untreated trees. The bio-fertilizers were applied as N-fixing bacteria (150 g/tree) was inculated in early March of each season, or amino acid mixture (1.5%) was applied three times, at 70% of full bloom, 21 days after full bloom, and a month later in comparison to a non-fertilized trees (control). The cultivar used was Kalamata, a dual-purpose cultivar for oil and table olives whose value increases when processed as table olives. The results indicated that the goat manure followed by olive pomace significantly enhanced photosynthetic pigments (chlorophyll a, b, and carotenoids), leaf mineral contents (N, P, K, Ca, Mg and Fe), tree canopy volume, number of flowers per inflorescence, number of inflorescences per shoot, initial fruit set, fruit retention. For fruit quality, fruit length and width, fruit weight, and total fruit yield was increased compared to the non-fertilized control. Likewise, The bio-fertilizer N-fixing bacteria followed by the amino acid mixture significantly improved all of the aforementioned parameters. Accordingly, it is recommended, both environmentally and economically to utilize organic and bio-fertizers, particularly goat manure combined with N-fixing bacteria, in low-fertility soil to sustain olive production as well as reducing mineral fertilization.     

Polycation-induced fusion of negatively-charged vesicles

Sonicated vesicles of 20-50 nm in diameter consisting of neutral phospholipids and a variety of acidic phospholipids were interacted with polylysine, cytochrome c, Ca2+ and Mg2+. The addition of polycations caused massive aggregation accompanied by an increase of membrane permeability as determined by leakage of fluorescent dye. Aggregation was followed by fusion of the vesicles into structures that in some cases exceeded 1 micron in diameter. Polylysine induced aggregation and appreciable fusion at charge ratios (polylysine/phospholipid) of 0.5-2, while divalent cations did so only at charge ratios (cation/phospholipid) greater than 10. Aggregation and fusion induced by polylysine were dependent also on the size of the polycation, i.e., the longer the molecule the less needed to induce similar aggregation. It appears that, due to the concentration of charges on a single molecule, polylysine is at least an order of magnitude more effective than divalent cations at inducing fusion of membranes. Cytochrome c induced fusion of similar vesicles at moderately acidic pH (pH 4.2).